1.Field of the Invention
The present invention relates to an improvement of a graphic data processing apparatus using a computer generally called a CAD (Computer Aided Design) system or a CAD/CAM (Computer Aided Design/Computer Aided Manufacturing) system.
2. Description of the Prior Art
FIG. 1 is an illustration showing an example of a display screen of a conventional CAD/CAM system. Referring to FIG. 1, operation for displaying graphic data such as a graphic form, characters or symbols on the display screen by using the conventional CAD/CAM system will be described.
A menu area 12 is provided for example in a lower portion of the display screen 10. Ten commands at maximum for example can be displayed at a time in the menu area 12. A user selects a desired command, if any, out of the commands displayed in the menu area 12. If there is not any desired command among the displayed commands, the user advances the display in the menu area 12 to search for a desired command in a manner of turning over display pages whereby the desired command is selected.
More specifically stated, in order to draw a circle for example, operation is to be performed in the following manner. First of all, the following commands are displayed in the menu area 12:
"1/ layer, 2/ change of frames, 3/ setting of a reference, 4/ cancellation of the reference, 5/ zoom, 6/ drawing, 7/ next item, 8/ menu"
The user designates the command "6/ drawing" by using a pointing device such as a mouse, a light pen or a cursor. Then, the following commands appear in the menu area:
"1/ line segment, 2/ continuous line, 3/ auxiliary line, 4/ circle, 5/ cross, 6/ arc, 7/ sector, 8/ spline, 9/ next item, .circle. 10 rise"
appear in the menu area 12. Thus, if the command "4/ circle" is designated by the pointing device, a command mode for drawing a circle is set, whereby a program for drawing a circle is read out.
If the user wants to draw "characters", he designates the command "9/ next item" appearing in the menu area 12 and changes display pages repeatedly until a desired command, namely, a command "characters" appears.
After having set the desired command mode, for example, the command "circle", the user designates, by using the pointing device, a place where a circle is to be drawn on a graphic display area 14 of the display screen 10. In the case of drawing a "circle", the user designates for example a center point (center coordinates) and a radius by using the pointing device. As a result, the circle is drawn. Attributes of the circle thus drawn, namely, data as to whether the circle is represented by a solid line, a dotted line or a chained line, and data as to the color of the line, the thickness of the line etc. are displayed in an attribute display area 16. It is also possible to change attributes of the thus drawn circle.
The number of commands for data processing increases, as performance of a CAD/CAM system becomes high. Accordingly, in the case of command display using the menu area 12 where only about less than ten commands can be displayed at a time, tens of pages for display of commands are required. As a result, it takes much time and labor to search for a desired command.
If the user knows which page contains which commands, the commands can be searched for relatively smoothly. However, in order to do so, the user needs to have much skill in use of the apparatus.
On the other hand, there is a system for inputting commands from a tablet 18 (as shown in FIG. 1) instead of the menu area 12. However, in this system for inputting commands by the tablet 18, it is not easy to search for a desired command out of all of the commands displayed on the tablet 18, for example, more than 100 commands, which involves disadvantages that much time is required for selection of desired commands.
In addition, in either system using the menu area 12 or the tablet 18, a content of each command is often expressed by an extremely short abbreviation. For example, a command indicating "draw a straight line" is expressed as "LN" and a command indicating "draw a circle" is expressed as "CR". Therefore, if such a command display method using abbreviations is adopted, training for having knowledge of contents of the commands is also required.